Audio recorders for use in conferences, business meetings and the like have evolved in recent years from relatively large, heavy devices using motor driven magnetic tapes to lightweight portable units which may be hand held and are powered by small batteries. Recently, solid state memories employing integrated circuits have supplanted tape recorders in many applications resulting in even smaller and lighter-weight units.
These integrated circuit recorders may record analog values representing the instantaneous amplitude of the sound reaching the unit's microphone or the microphone output may be digitized and stored as binary values. Digital compression/decompression circuits may be employed to increase storage capacity for a fixed memory size. Often these recorders employ sound responsive switches to reduce the battery drain when there are no sounds to be recorded.
These recorders may operate on a first-in first-out basis so that the recorder stores the most recently captured sounds and discards signals or overwrites representative of the oldest sounds so that the memory capacity is not exceeded. For example, if a memory has a capacity for storing ten minutes of sound, when the memory is full the system continues to record the most recently generated sounds at the expense of signals stored in the recorder representing the oldest sounds so that at any time the most recently recorded ten minutes of sounds are stored.
In certain recording situations most of the sounds being recorded, be they voice or music or the like, need not be preserved, but from time-to-time sounds will be generated that the operator of the recorder desires to preserve and later play back and possibly transcribe. For example, in a business meeting, court proceeding, musical rehearsal or the like there may be no need to record the entire proceedings, but occasionally a statement is made or a musical section is played that the operator, after hearing the sounds, deems it important to preserve. The present invention is directed towards such usages.